1. Field of the Invention
The invention relates to an electronics module configured for insertion into a carrier unit and having arranged on a rear face a coding pair comprising a first coding part and a second coding part, where the first and the second coding part are configured according to the lock-and-key principle, and the first coding part being arranged snapped into place in the rear side, while the second coding part is removably arranged around the first coding part.
2. Description of the Related Art
Particularly in the case of automation devices, electronic control devices for automation engineering applications are often constructed in two parts. Preferably, the first part comprises an electronics module having electronic components that are required for solving control tasks. The second part is referred to as a carrier unit and serves among other things for realizing a modular configuration consisting of a plurality of electronics modules to form an automation component. In addition, the carrier unit has connecting terminals for signal lines coming from a process that is to be automated. By virtue of this two-part design, it is possible to replace a defective electronics module quickly, particularly in the event of a fault, because there is no need to disengage the wiring of the signal lines and reconnect the signal lines subsequently. Furthermore, the two-part construction affords advantages during the building of a plant that is to be automated, because the carrier unit can be installed and wired first and the corresponding electronics modules can be inserted later.
A process connector for connecting process lines to an input/output module of the control system is known from DE 195 14 824 A1. Here, the process connector or, as the case may be, the input/output module has a coding element and a mating coding element. In existing systems of this type, it has proven beneficial to dispose an autonomously acting mechanical coding arrangement between the electronics module and the carrier unit. For that purpose, a two-part coding arrangement is mounted in a captive manner in the housing of the electronics module. In that arrangement, the first part snaps into place in the housing such that only destructive removal and/or removal via a tool is possible. The second part of the coding arrangement is joined to the first via a snap-fit connection, preferably in a form- and force-fit manner, such that it cannot become detached of its own accord during “normal” handling of the electronics module. When the electronics module is plugged into the carrier unit, the second part of the coding arrangement snaps into place in the carrier unit and remains in the carrier unit when the electronics module is again withdrawn from the carrier unit. This ensures that when a defective electronics module is replaced at this position in the carrier unit, only an electronics module having identical coding can be reinserted.
However, when it comes to building automation components that must necessarily guarantee failsafe operation, such as petrochemical industry, the principle of the mechanical coding arrangement is no longer fit for its purpose.